Caribbean lost half its corals since 1970s

Scientists say that reefs could recover with a reintroduction of species such as parrotfish.

The main culprit for coral loss is overfishing of parrotfish, says UNEP.

The Caribbean has lost at least half its coral reefs since the 1970s, says a new report by the United Nations Environment Programme (UNEP). And the main culprit, it adds, is overfishing — in particular, the loss of parrotfish.

Large parrotfish graze down algae that can otherwise smother corals. If the trend in overfishing continues, Caribbean reefs — which account for about a tenth of the world’s corals — could all but vanish in 20 years, the report predicts.

Mass die-out

The mass die-out of another key marine grazer, the sea urchin, has also hit corals hard. A pathogen introduced from ballast water discharged from bulk carrier ships is thought to have wiped out sea urchins in the 1980s.

Marine grazers also seem to make reefs more resilient to hurricanes. For instance, the overfished reefs in the Central Barrier in Belize declined by half after three hurricanes, while the better protected reefs in Bermuda saw no coral loss after four hurricanes since 1984.

Ocean warming and acidification are drivers of coral bleaching and degradation too, but “local stressors” such as overfishing and tourism have been the most responsible for the catastrophic decline of Caribbean corals, says the report.

Hope of repair

But there is hope yet for these ecosystems. Scientists say that reefs could recover with a reintroduction of species such as parrotfish.

While these new insights could be useful in managing reefs around the world, local realities can vary widely, lead author Jeremy Jackson, a senior advisor to the International Union for the Conservation of Nature (IUCN), told The Hindu by email. “For example, surgeonfish are more important grazers than parrotfish throughout much of the Indo-West Pacific. So local knowledge is important.”

Reefs around the world are indeed similarly shrinking, he added. “The Great Barrier Reef in Australia has lost half to three-fourth of its live coral, and reefs in the East African coast have shown great losses too.”

The report on the “Status and Trends of Caribbean Coral Reefs” is co-authored by teams from the Global Coral Reef Monitoring Network, IUCN and UNEP.

( The Correspondent participated in the United Nations Environment Assembly in Nairobiat the invitation of UNEP. )